Temperature responsive switch

ABSTRACT

This invention relates to a temperature switch and more particularly to a temperature responsive switch used in a catalytic converter generally found in internal combustion engine exhaust systems. The temperature switch is an independent selfcontained unit that is mounted directly on the converter and has a sensing element that extends into the converter to activate switch contacts to provide an initial signal, as well as a second signal that the catalyst within the converter may become ineffective due to deterioration of the catalyst and therefore maintenance of the converter is required. The signal could also be used to activate bypass means in or adjacent to the converter.

United States Patent [191 Zelenka Jan.8, 1974 TEMPERATURE RESPONSIVESWITCH Donald J. Zelenka, Flushing, Mich.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Dec. 4, 1972 [21] Appl. No.: 311,933

[75] Inventor:

Primary Examiner-Roy N. Envall, Jr. Attorney-Sidney Carter et al.

[5 7] ABSTRACT This invention relates to a temperature switch and moreparticularly to a temperature responsive switch used in a catalyticconverter generally found in internal combustion engine exhaust systems.The tempera: ture switch is an independent self-contained unit that ismounted directly on the converter and has a sensing element that extendsinto the converter to activate switch contacts to provide an initialsignal, as well as a second signal that the catalyst within theconverter may become ineffective due to deterioration of the catalystand therefore maintenance of the converter is required. The signal couldalso be used to activate bypass means in or adjacent to the converter.

2 Claims, 1 Drawing Figure TEMPERATURE RESPONSIVE SWITCH This inventionrelates to a temperature responsive switch having a sensing elementinserted into a catalytic converter to provide a warning signal that theconverter may not be functioning properly because the catalyst maybecome ineffective due to deterioration. Problems of air pollution frominternal combustion engines and the use of catalytic converters in theexhaust system of such engines to minimize air pollution has led to therequirement for a simple and inexpensively manufactured temperaturesensing device to be used within the converter to detect failure of thecatalyst in the converter. Most of the similar devices available aredelicately constructed as well as expensive to manufacture and thereforeimpractical for use as temperature switches in the automobileapplication. Similar devices available do not perform properly in therigorous environment and the rigorous use that they are put to wheninstalled in automobile converters and further any sensors practical foruse are very costly and complex to produce by mass productiontechniques.

Accordingly, it is an object of the present invention to provide asimple, reliable and inexpensive switch having means for sensingexcessive temperature in the converter as well as the failure of thecatalyst in the converter.

Another object is to provide a switch that gives two signals atdifferent time intervals.

A further object is to provide a temperature device that is directlyconnected to the converter and has a sensing element on a probe withinthe converter that is constructed of the same catalyst material found inthe converter.

Another object is to provide a temperature switch having interchangeablesensing means.

Another object of the invention is to provide a temperature switch thatcan be produced and assembled by mass production techniques.

A further object is to provide a temperature sensing switch that iscompact and self-contained and therefore can be manufactured and adaptedfor use as an assembly for easy insertion into a converter.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing wherein a preferred embodiment of the present invention isclearly shown.

The FIGURE shows a cutaway sectional view of the preferred embodiment ofthe invention.

Referring to the drawing, there is shown a switch housing generallyconstructed of a one-piece body member 12 that may be made of stainlesssteel or the like, having attachment means 14 in the form of a threadedneck portion 16 at one end thereof.

Assembled within the body 12 is a tube assembly 18 that has a flared outattaching portion 20 at one end thereof that rests on a shoulder 22 inbody 12 and makes electrical contact with the body. Tube assembly 18extends through the neck portion 16 and is of sufficient length toextend into the catalyst bed of the converter, when the housing isattached to the converter. Tube assembly 18 and the flared attachingportion 20 are made of lnconel or similar type metals in order towithstand the heat within the converter. Electrically connected to tubeassembly 18 are a set of contacts 24 that may be formed directly on theflared portion 20 of the tube or may be independently formed andattached thereto by some means such as welding, brazing or the like. Asecond set of contacts 26 are located opposite contacts 24 and areattached to a flanged or turned over portion 27 on a movable inner oractuator tube member 28 that may also be made of stainless steel orlnconel as is tube 18. Spring 30 rests on the flanged portion 27 andelectrically connects the two sets of contacts, when they are closed, toa terminal ring 32 having a connector 34 that extends through the body12 at the end opposite from the threaded neck portion 16.

Within tube 28 and insulated therefrom by a ceramic insulator sleeve 29or other known insulator means is a capillary tube 31 of the type wellknown in the art, having a diaphragm 33 within body 12, with a singlecontact 35 thereon. Diaphragm 33 is made of corrugated metal or similarmaterials in order to withstand the high operating temperatures of theconverter. Tube 31 is held in position within body 12 by a tube holdingmember 37 that has a generally cup shaped or U shaped portion extendingdownwardly into body 12, within spring 30. Opposite contact 35 is asecond single adjustable contact 39 that is connected to a terminal 41having connector 43 thereon. Contact 39 and terminal 41 are electricallyinsulated from the tube holding member 37 by a ceramic insulator or thelike and are held in position on the insulator by a hollow rivet 45 orsimilar means having threads therein to receive the adjustable contact39. Diaphragm 33 is held in the cup shaped member 37 with the contacts35,39 being normally open.

Contacts 26, spring 30 and the terminal 32 are electrically insulatedfrom the body 12 by insulating means 36, 38. insulator 36 is adjacentthe inside wall of body 12 and insulator 38 is located between tubeholding member 37 and terminal ring 32. Insulator means 36 can be aceramic insulator, and insulator 38 can be made of mica, for example.The components assembled within the body 12 are held in place byrolled-over portions 42 formed on the body 12 that bear against flanges47 on the tube holding member 37 and the insulating means 31, 38 and 40.

Actuator tube 28 generally extends the full length of the tube assemblyand engages a second rod 48 that is formed of a catalyst material whichis inserted in a tube or can member 50. The catalyst material that makesup the second rod 48 is the same as the catalyst material found in theconverter. It is understood that metal or other means having a meltpoint or deterioration point the same as the catalyst could be used. Thelength of the tubular formed catalyst 48 is such that it forces actuatortube 28 upwardly into the body member 12 to push the spring towardterminal 32 to maintain contacts 24,26 in a normally open position.Actuator tube 28 is therefore spring biased in a downward direction andthe contacts are normally open. Can member 50 is connected to tubularmember 18 by a bayonet type connection 52. Bayonet connector 52 isgenerally formed of a pair of ear members 54 on tubular member 18 andmating pin members 56 on the can 50 with such connectors being wellknown in the art.

In operation the housing 10 is screwed into a catalytic converterforming a path to ground through neck 16. The tubular member 18 havingactuator tube 28 therein and can 50 attached thereto, extend into theconverter and into the catalyst bed. The length of the catalyst rod 48determines the distance that the contacts are apart and thereforedetermines the length of time the catalyst within the converter can beexposed to high temperature without damage. If the catalyst is exposedto high temperature beyond this period, the catalyst in the converterwill begin to deteriorate. The catalyst rod 48 being of a smaller volumethan the catalyst bed in the converter will deteriorate faster than thecatalytic bed and due to deterioration will shrink causing actuator tube28 urged by spring 30, to move downwardly. When the catalyst rod 48 hasdeteriorated to the point where the converter could be damaged, contacts24,26 close to provide a signal through connector 34 and ground, to atelltale or the like that the catalyst within the converter is in dangerof deterioration and therefore the converter should be serviced. Uponthe converter being serviced, which would generally be at time thatreplacement of the catalyst is required, the can member 50 isdisconnected from the tubular member 18 and catalyst rod 48 within can50 is replaced or a new can member containing the catalyst rod could bereplaced as a unit.

Capillary tube 31 provides a second circuit for signal means whichcircuit can also be used to energize a telltale or light or similarmeans at a later or more critical point than the first signal generatedbecause of the deterioration of catalyst rod 48. The circuit may also beused to control a converter bypass system. A solenoid operated bypassvalve or the like can be controlled to open when the temperature wouldbe damaging to the catalyst and close when the temperature drops to aproper catalyst operating range. In operation, the capillary tube 31 anddiaphragm 33 are responsive to changes in temperature at the bulb end ofthe capillary tube. Increasing temperature causes the diaphragm havingcontact 35 thereon to move upward and make contact with contact 39.Decreasing temperature causes it to move away from contact 39 and breakcontact. This is achieved by the respective expansion and contraction ofthe filler material inside the capillary tube and diaphragm assembly. Aspecific switch point can be achieved by adjusting contact 39 to makecontact with the contact 35 on the diaphragm at a specific temperaturedesired. The electrical circuit is from connector 43 to contact 39 tocontact 35 on the diaphragm attached to the end of the capillary tube tothe tube holder 37 to the body 12 which is ground.

It is readily apparent that the temperature switch is an easilyconstructed simple device that is easily assembled and has a replaceablesensor at one end that can be readily serviced at minimal cost.

While the embodiments of the invention as herein disclosed constitute apreferred form, it is to be understood that other forms could beadopted.

1 claim:

1. A temperature responsive electrical switch comprising: a body havingattachment means thereon; a first tubular member having one end in saidbody in electrical contact therewith, and the other end extendingtherefrom; first contact means on the one end of said first tubularmember; a second tubular member within said first tubular member havingsecond contact means opposite said first contact means; spring meanselectrically connecting said second contact means to a terminal on saidbody; said second tubular member being in contact with an expendablesensing means at the end opposite said second contact means thereon,said expendable sensing means mounting said first and second contactsopen; insulator means electrically insulating said contacts, springs,and terminals from said body; and a temperature responsive means withinsaid second tubular member electrically insulated therefrom and havingan expandable diaphragm at one end; contact means on said diaphragm;third contact means opposite said contact means on said diaphragm beingwithin a terminal on said body.

2. A temperature responsive electrical switch adapted to be used in acatalytic converter to detect catalyst failure comprising: a body havingattachment means thereon; a first tubular member having one end in saidbody in electrical contact therewith, and the other end extendingtherefrom; first contact means on the one end of said first tubularmember; a second tubular member within said first tubular member havingsecond contact means opposite said first contact means; spring meanselectrically connecting said second contact means to a terminal on saidbody; insulator means electrically insulating said contacts, springs,and terminals from said body; said second tubular member being incontact with a first temperature responsive expendable rod formed of asubstantially similar catalyst as used in the converter; said expendablerod being held in a container that is attached to said first tubularmember by removable connector means, and being of sufficient length toforce said second tubular member to maintain said first and secondcontacts in a normally open position whereby upon catalyst failure inthe converter said catalyst rod shrinks to cause the first and secondset of contacts to close and provide a signal and a second temperatureresponsive capillary tube means within said second tubular memberelectrically insulated therefrom and adapted to provide a secondindependent signal; having a metal diaphragm at one end with a capillarytube holding member adjacent said diaphragm and being attached to saidbody to hold said capillary tube within said second tubular member;contact means on said diaphragm; third contact means opposite saidcontact means on said diaphragm being within a terminal on said bodywith said terminal being insulated from said tube holding member.

1. A temperature responsive electrical switch comprising: a body havingattachment means thereon; a first tubular member having one end in saidbody in electrical contact therewith, and the other end extendingtherefrom; first contact means on the one end of said first tubularmember; a second tubular member within said first tubular member havingsecond contact means opposite said first contact means; spring meanselectrically connecting said second contact means to a terminal on saidbody; said second tubular member being in contact with an expendablesensing means at the end opposite said second contact means thereon,said expendable sensing means mounting said first and second contactsopen; insulator means electrically insulating said contacts, springs,and terminals from said body; and a temperature responsive means withinsaid second tubular member electrically insulated therefrom and havingan expandable diaphragm at one end; contact means on said diaphragm;third contact means opposite said contact means on said diaphragm beingwithin a terminal on said body.
 2. A temperature responsive electricalswitch adapted to be used in a catalytic converter to detect catalystfailure comprising: a bodY having attachment means thereon; a firsttubular member having one end in said body in electrical contacttherewith, and the other end extending therefrom; first contact means onthe one end of said first tubular member; a second tubular member withinsaid first tubular member having second contact means opposite saidfirst contact means; spring means electrically connecting said secondcontact means to a terminal on said body; insulator means electricallyinsulating said contacts, springs, and terminals from said body; saidsecond tubular member being in contact with a first temperatureresponsive expendable rod formed of a substantially similar catalyst asused in the converter; said expendable rod being held in a containerthat is attached to said first tubular member by removable connectormeans, and being of sufficient length to force said second tubularmember to maintain said first and second contacts in a normally openposition whereby upon catalyst failure in the converter said catalystrod shrinks to cause the first and second set of contacts to close andprovide a signal and a second temperature responsive capillary tubemeans within said second tubular member electrically insulated therefromand adapted to provide a second independent signal; having a metaldiaphragm at one end with a capillary tube holding member adjacent saiddiaphragm and being attached to said body to hold said capillary tubewithin said second tubular member; contact means on said diaphragm;third contact means opposite said contact means on said diaphragm beingwithin a terminal on said body with said terminal being insulated fromsaid tube holding member.